Regulation of specific propein synthesis at the translational level will be studied in the hen and immature chick oviduct. In this tissue a single protein, ovalbumin, accounts for 50 - 60 percent of the total synthesized, and estrogen is required for both cytodifferentiation of the tissue in immature chicks and maintenance of specific protein synthesis. Part one of this study will be an investigation of the protein synthesis initiation factor responsible for recognizing ovalbumin mRNA. An assay will be developed for detecting the initiation factor (IF3) based on the factor-dependent binding of radioactive ovalbumin mRNA to 405 ribosomal subunits (40S initiation complex). Using this assay, the proteins(s) will be purified and tested for recognition of other oviduct messengers. Part two will be an investigation of the stability of mRNA in the oviduct. The half-life of active ovalbumin mRNA will be determined by administering drugs that inhibit RNA synthesis or cause defective RNA synthesis in vivo and then following the decay in ovalbumin mRNA active as assayed in a cell-free system derived from rabbit reticulocytes or Krebs II ascites tumor cells. The degradation rate of ovalbumin mRNA will be compared to that of other oviduct messengers in various physiological states of the oviduct.